The Fowler 54-565-233 High-Accuracy Ultima Bore Gauging System has a measurement range of 7.878 to 8.27" and is accurate to + or - 0.00006". Resolution is 0.00001" and the measuring depth is 3.15". The gauge has constant spring pressure for repeatability and Bower's FastFit measuring heads for rapid measurement. It uses a three-point contact system for the detection of lobing or triangular form error, and ceramic contact points provide high durability and stability with regard to thermal expansion. The Ultima system requires connection to a Sylvac or multiplexer display unit.This product has 1 year warranty offered by Fowler High Precision. If you experience any problem contact Fowler directly for warranty claims.